One of the most common uses of agricultural tractors is to tow implements through agricultural fields to cultivate the soil. There are many such implements, and many of these implements have the capability of being raised or lowered with respect to the ground. This is often desirable to control the depth of cultivation performed by various ground-engaging devices attached to the frame of the implement. As the frame is lowered closer to the ground, the ground engaging devices dig deeper into the soil. As the frame is raised higher above the ground, the ground engaging devices dig more shallowly into the soil.
In the most common arrangement, the implement has one or more wheels that are pivotally coupled to the frame of the implement. The position of these wheels is varied by controlling the extension or retraction of a hydraulic cylinder. By extending or retracting the hydraulic cylinder, the operator of the tractor can raise and lower the frame of the implement with respect to the ground.
Typically, the operator has a manually operable device in the cab of the tractor that he manipulates to raise and lower the implement accordingly. The operator grasps the device and moves it through a range of positions, each of said positions having a corresponding implement height. To move the implement to any specific height, the operator merely grasps the device and moves it to the corresponding position.
Moving the lever will set a preferred height of the implement. It will not, however, keep the implement in that position. To maintain the implement in the selected position, the operator must periodically turn his head around and look at the implement. If the implement has drifted away from the preferred height, the operator must grasp the input device and again manipulate it to shift the implement back to the preferred position. Therefore, even in systems in which the operator can adjust the implement height, he must still visually monitor the position of the implement and “tweak” his operator input device to keep the implement at that precise position.
The continuing requirement to regularly turn his head and inspect the implement adds yet another task to an already task-burdened tractor operator. He must look forward to make sure the tractor is pointed in the proper direction. He must look at his various gauges to determine the tractor is operating properly. He must look at other gauges to make sure that the implement is operating properly. In addition, he must look behind regularly to make sure that the implement is engaging the ground properly.
All of this activity and calculation requires a great deal of concentration on the part of the tractor operator. Anything that can automate these tasks and reduce the number of activities the operator must constantly monitor would be beneficial.
What is needed, therefore, is a system for controlling the heights (and depth of ground engagement of) of an implement towed by an agricultural tractor.
What is also needed is a system for easily changing the desired position of the implement towed by the tractor.
What is also needed is a system for permitting the operator to easily override automatic control of implement height, and to quickly return to automatic control of implement height when desired.
These and other advantages are provided by the system and method described below.